Instrument for measuring saliva viscoelasticity to determine female fertile period

ABSTRACT

An instrument for measuring saliva viscoelasticity to determine a woman&#39;s fertile period comprised of a sheath, a cap, and an escapement. The instrument includes a barrel with a pair of elongated slots, a piston within the barrel with protrusion that extend into and beyond the slots, and a sleeve over the barrel with a pair of spiral groove into which the protrusions fit. As the sleeve rotates about the barrel, the grooves spiral up or down, causing the piston to move axially within the barrel. A central cavity within the barrel includes a constricted throat near the top end. The escapement is a U-shaped strip of plastic that fits into the cavity and attaches at its cross portion to the piston. The ends of the escapement arms have mating surfaces that are roughened so that the saliva sample will fracture before it separates from the surfaces. As the escapement is pulled into the cavity, the throat operates to press the mating surfaces together. After the throat is passed, the escapement cross portion acts as a spring to pull the mating surfaces apart against the viscoelasticity of the saliva. The amount of time it takes for the saliva to fracture under pressure from the spring is measured and used to indicate whether the user is in her fertile period or not.

GOVERNMENT FUNDING

The research involved in this application was funded in part by theNational Institutes for Health, grant number 1 R41 HD32218-01. Theintellectual property rights of the applicant and the government of theUnited States of America are governed by Title 37 Code of FederalRegulations Part 401.

RELATED APPLICATION

This application is a continuation-in-part of abandoned application Ser.No. 08/589,138, entitled INSTRUMENT FOR MEASURING SALIVA VISCOELASTICITYTO DETERMINE FEMALE FERTILE PERIOD, filed on Jan. 19, 1996, which is acontinuation-in-part of application Ser. No. 08/524,741, now U.S. Pat.No. 5,640,968, entitled INSTRUMENT FOR MEASURING SALIVA VISCOELASTICITYTO DETERMINE FEMALE OVULATION TIME, filed on Sep. 7, 1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the measurement of the viscoelasticityof saliva, and more particularly, to a device for the measurement ofsaliva viscoelasticity in order to determine a woman's fertile period.

2. The Prior Art

It has been known that the cervical mucus of a female has a maximumfluidity just before ovulation, where ovulation is defined as the momentthat an ovum is released from the follicle. This knowledge lead to theapplicant's previous activities in the development of techniques formonitoring the viscoelasticity, or tackiness, and other properties ofcervical mucus as a predictor of time of ovulation and to improvementsin rheometer or viscometer apparatus for measuring such viscoelasticproperties. See, for example, L. E. Kopito and H. J. Kosasky, "TheTackiness Rheometer Determination of the Viscoelasticity of CervicalMucus," Human Ovulation, edited by E. S. E. Hafez, Elsevier,North-Holland Biomedical Press, 1979, pp. 351 et seq., and U.S. Pat.Nos. 4,002,056 and 4,167,110. Though the viscoelasticity of the cervicalmucus has several small dips in its characteristic curve of viscosityversus time preceding, during, and following ovulation (a four-dayperiod), there is a distinct identifiable minimum viscoelasticity.Instruments designed to measure this effect are described in, forexample, U.S. Pat. Nos. 4,002,056 and 4,072,045.

Saliva is now known to undergo physiochemical changes during themenstrual cycle, including a change in its viscoelasticity. Especiallypronounced is the change in viscoelasticity of sublingual saliva, thesaliva found under the tongue. See, for example, S. S. Davis, "Saliva isViscoelastic", Experientia, 26: 1298, (1970), and R. H. Davis et al.,"Saliva Viscosity Reflects the Time of Ovulation", Experientia, 30: 911,(1974). As described in U.S. Pat. No. 4,779,627, issued on Oct. 25,1988, to the present applicant, and entitled PROCESS AND APPARATUS FORDETERMINING FEMALE OVULATION TIME BY MEASUREMENT OF SALIVAVISCOELASTICITY, the applicant previously discovered that sublingualsaliva has a unique and reliably measurable minimum in viscoelasticitythat is coincident with the ovulation cycle and its surge of estradiol.

There are devices on the market for measuring viscoelasticity todetermine ovulation time, but these devices are designed to use cervicalmucus as a sample medium, rather than saliva. The viscoelasticity ofcervical mucus is an order of magnitude higher than that of saliva.Consequently, devices designed to use cervical mucus as a sample mediumare typically not sensitive enough to use saliva as a sample.

The above-identified U.S. Pat. No. 4,779,627, in addition to disclosinga process for determining female ovulation time by measuring salivaviscoelasticity, discloses a device for measuring the viscoelasticity ofthe sublingual saliva. The device has a shape somewhat like a syringe,with an outer cup, an inner cup concentric with and located within theouter cup, and a plunger. A roughened surface on the end of the plungerholds the saliva sample. The plunger is inserted into the inner cupuntil the saliva sample is compressed against the bottom of the innercup. A predetermined amount of weight pulls the inner cup downward,stretching the saliva sample. If the viscoelasticity of the saliva islow, the saliva sample will fracture, causing the inner cup to fall tothe bottom of the outer cup. An indicator at the bottom of the outer cupindicates that the inner cup has fallen to the bottom which, in turn,indicates that ovulation will soon take place. If, however, theviscoelasticity of the saliva is high, the saliva sample will hold theplunger and inner cup together so that the inner cup will not fall tothe bottom, indicating that ovulation will not take place in the nearfuture.

This device has several disadvantages. The first disadvantage is thatthe device can only be used conveniently for one person. The amount ofweight that pulls the inner cup downward is selected for a specificperson. There must have been a sublingual saliva sample measured fromthe same person at a time when the sublingual saliva is known to havethe minimum viscoelasticity in order to select the amount of weight.

The second disadvantage is that the device must be taken apart in orderto take a sample. The plunger must be removed from the inner cup beforebeing inserted in the mouth to obtain a saliva sample. This has thepotential for the person to easily contaminate the saliva sample byincorrectly reinserting the plunger after taking the sample,invalidating the measurement.

SUMMARY OF THE INVENTION

One object of the instrument of the present invention is to provide aninstrument for measuring saliva viscoelasticity to determine a woman'sfertile period that is easy and convenient to use.

Another object is to overcome the need to calibrate the instrument to anindividual.

A further object of the present invention is to reduce the possibilityof contamination of the saliva sample prior to measurement.

The instrument of the present invention for measuring salivaviscoelasticity to determine a woman's fertile period is comprised of asheath, a cap, and an escapement. The sheath includes a barrel, apiston, and a sleeve. The barrel is a hollow cylinder with a pair ofelongated, opposed slots. The piston resides within the barrel and has apair of protrusions that extend into and beyond the slots. The sleevefits over the barrel and rotates about the barrel. The inside sur faceof the sleeve includes a pair of spiral grooves in which the pistonprotrusions fit, so that, as the sleeve rotates, the grooves spiral upor down, causing the piston to move axially within the barrel.Alternatively, the protrusions are replaced by ball bearings for a moresmooth piston motion. The cap fits over the top end of the sheath inorder to protect the inner components of the instrument.

The barrel includes a central cavity that is rectangular at the top end.The cavity extends into the sheath, initially decreasing in width andthen increasing in width, to form a constricted throat. The rectangularcavity eventually opens into a circular cavity, the space in which thepiston moves.

The escapement fits in the rectangular cavity and attaches to thepiston, preferably by a removable connector. The escapement is anelongated U-shaped strip of plastic or composite that is either composedof or coated with an electrically-conductive material. Attached to ormolded into the upper ends of the arms are a pair of opposed plates thathave mating surfaces. The arms also include a pair of opposed elbows.The cross portion forms a spring that forces the mating surfaces awayfrom each other.

In operation, the piston is initially at the top of the circular portionof the cavity, and the escapement is attached to it and in therectangular portion of the cavity. The mating surfaces are outside ofthe cavity. The user dips the mating surfaces into the saliva pool underher tongue. The surfaces are roughened so that the saliva will fracturebefore it separates from the surfaces. After the saliva sample is taken,the user rotates the sleeve to pull the escapement into the cavity. Asthe elbows pass through the throat, the mating surfaces are pressedtogether, compressing the saliva sample. As the elbows pass out to thethroat, the spring applies a force to pull the mating surfaces apart. Atthe same time, the elbows close a start switch on a timer circuit, thecomponents of which are located either internal or external to thesheath. As the escapement continues downward movement to the bottom ofthe cavity, the mating surfaces remain held together by theviscoelasticity of the saliva. Eventually, the force of the springovercomes the viscoelasticity of the saliva and the mating surfacesseparate. When that happens, the elbows close a stop switch on thetimer, and the timer indicates the result of the measurement on a pairof light-emitting diodes or a liquid crystal display.

Other objects of the present invention will in part be obvious and willin part appear hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and object of the presentinvention, reference is made to the accompanying drawings, wherein:

FIG. 1 is a perspective view of the instrument of the present invention;

FIG. 2 is an exploded, partial phantom view of the sheath of FIG. 1;

FIG. 3 is a top view of the sheath;

FIG. 4 is a side cross-sectional view of the sheath;

FIG. 5 is an electrical schematic of the timing circuit;

FIG. 6 is a side view of the escapement of FIG. 1;

FIG. 7 is a perspective view of one embodiment of the escapement/pistonconnector;

FIG. 8 is a perspective view of another embodiment of theescapement/piston connector;

FIG. 9 is a cross-sectional view of the first step of operation;

FIG. 10 is a cross-sectional view of the second step of operation;

FIG. 11 is a cross-sectional view of the third step of operation;

FIG. 12 is a cross-sectional view of the fourth step of operation;

FIG. 13 is a low-power microphotograph of a plate surface;

FIG. 14 is a high-power microphotograph of a plate surface; and

FIG. 15 is a curve showing the relationship between the viscoelasticityof saliva and ovulation time.

DETAILED DESCRIPTION

The Instrument

The preferred embodiment 10 of the invention is shown in FIGS. 1-5. Itis comprised of three basic components: a sheath 12, a cap 14, and anescapement 20.

FIGS. 2 and 4 show an exploded and cross-sectional view of the sheath12. It includes three components: a barrel 22, a piston 24, and a sleeve26. The barrel 22 is a hollow cylinder with a pair of opposed slots 28near or at the bottom end 30 (only one slot is shown in the figures).The slots 28 are elongated parallel to the axis of the barrel 22. Thepiston 24 is also a cylinder that fits within the barrel 22. The piston24 has an outside diameter slightly smaller than the inside diameter ofthe barrel 22 so that the piston 24 fits snuggly within the barrel 22,but also can reciprocate within the barrel 22. The outer surface of thepiston 24 includes a pair of opposed protrusions 32 (only one is shown)that slide within the slots 28 as the piston 24 reciprocates. Theprotrusions 32 extend beyond the outer surface of the barrel 22. Thesleeve 26 is also cylindrical and fits over the barrel 22. The insidediameter of the sleeve 26 is slightly larger than the outside diameterof the barrel 22 so that the sleeve 26 can rotate about the barrel 22.The inside surface of the sleeve 26 includes a pair of interlaced spiralgrooves 34 (only one of which is shown). The protrusions 32 residewithin these grooves 34 so that, as the sleeve 26 rotates, the grooves34 spiral up or down, depending upon the direction of rotation. Becausethe protrusions 32 are limited to axial motion within the slots 28, thepiston 24 is pushed axially within the barrel 22. The range of thepiston's motion is limited by the length of the slots 28, where theprotrusions 32 make contact with the slot ends 36 and cannot move anyfarther.

In an alternative embodiment, and in order to provide a smoother motionfor the piston, each protrusion 32 is replaced by a depression and aball bearing. The ball bearing sits in the depression and rides withinthe spiral groove as the sleeve turns.

The central cavity 40 of the sheath, when viewed from the open end ofthe sheath 12, as in FIG. 3, is rectangular in shape and the rectangleis centered about the axis of the sheath 12. The narrow dimension of thecavity 40 is the slightly larger then the width of the escapement 20, asdescribed below. The cavity 40 extends into the sheath 12 a shortdistance, as at 44. Extending further into the sheath 12, the cavity 40decreases in size, as at 46, remains substantially constant, as at 48,for a short distance, and then increases, as at 50. The narrowing andwidening of the cavity 40 defines a throat 52. The cavity 40 continueswith a rectangular shape for a distance, as at 54, until it enlarges toa cylindrical shape in which the piston 24 operates, as at 56.

Within the sheath 12 is a timing circuit 60, a schematic diagram ofwhich is shown in FIG. 5. The timing circuit 60 is composed of a timer62, a pair of start panels 64, a pair of stop panels 66, a battery 68,and the two light-emitting diodes (LED's) 70, 72. The LED's 70, 72 aremounted within the wall of the sheath 12 so that they are visible by theuser. When the start panels 64 are electrically connected together, asdescribed below, the timer 62 begins timing. When the stop panels 66 areelectrically connected together, as described below, the timer 62 stopstiming. The timer 62 then compares the elapsed time to a predeterminedvalue, and if the elapsed time is greater, it momentarily energizes oneof the LED's 70, otherwise it momentarily energizes the other LED 72.The battery 68 supplies electrical power to the timing circuit 60.

Alternatively, various combinations of the timer 62, battery 68, andLED's 70, 72 are mounted on the outside of the sheath 12. Alternatively,the timing circuit includes a microprocessor for controlling the timeroperation and a liquid-crystal display (LCD), rather than a pair ofLED's, for displaying the results.

The cap 14 is shaped substantially like an inverted cup and is composedof a rigid plastic. It fits over the top end of the sheath 12 in orderto protect the inner components of the instrument 10. It can be retainedin any manner that is appropriate, such as by mating threads or frictionfit.

As shown in FIG. 6, the escapement 20 is a substantially elongatedU-shaped strip of plastic or composite 80 that is coated with anelectrically-conductive material. In an alternate configuration, thestrip 80 is an electrically-conductive plastic or composite. The strip80 is wide enough to prevent the arms 82 from twisting longitudinallywithin the cavity 40 in normal use. The arms 82 include a pair ofopposed elbows 84, which are created by three bends in the strip 80. Theupper bend 86 and the lower bend 88 angle approximately 45° outwardlyfrom the plane of the arm 82, forming the center bend 90 ofapproximately 90°.

The cross portion of the escapement 20 is at the inner extremities ofthe arms 82. The curve of the cross portion forms a spring 92, whichforces the arms 82 to pivot outwardly from a vertical position to ahorizontal position, as at 94. The amount of force exerted by the spring92 is dependent on the material of which the strip 80 is composed andthe thickness of the strip 80. The preferred force is described below.

In one embodiment of the escapement 20, at the outer extremity of eacharm 80 is a frame 96 into which are permanently mounted plates 100 by asubstantially waterproof adhesive. In a second embodiment, the plates100 are removably mounted so that the plates 100 may be discarded andreplaced. In a third embodiment, the plates 100 are integrally formedwith the arms 80. The plates 100 have mating surfaces 102, which aredetailed below.

In the preferred embodiment, the escapement 20 is removable so that itcan be replaced after each use. To facilitate removal and replacement,there is a connector 104 between the escapement 20 and the piston 24. Inone embodiment, shown in FIG. 7, the connector 104 is in the form of asnap, such as found on clothing, where the male component 106 is adheredto or molded into the spring 92 of the escapement 20 and the femalecomponent 108 is attached to the piston 24. In another embodiment, shownin FIG. 8, the piston 24 includes a pair of tongues 112 that curve upfrom the piston upper surface 114. The tongues 112 are weak enough sothat when the escapement 20 is pushed down onto them, they deflectdownwardly. As the spring 92 of the escapement 20 makes contact with thepiston 24, the tongues 112 snap back into normal position, holding theescapement between the tongues 112 and the piston 24. The escapement 20is removed by pulling it hard enough to bend the tongues 112 upwardlyaway from the piston surface 114.

FIGS. 9-12 detail, in cross-section, the internal operation of theinstrument 10. FIG. 9 shows the initial position of the piston 24 andescapement 20, which is at the upper limit of the piston 24.

In FIG. 10, the user has turned the sleeve 26 a short distance. Theaction of the throat surface 46 on the elbows 84 is a camming mechanismthat causes the mating surfaces 102 to make flush contact. This actioncauses the upper portions of the escapement arms 82 to deform outwardlyat the elbows 84. The amount of force holding the mating surfaces 102and, as a consequence, compressing the saliva sample, is related to theamount of elbow deformation. Preferably, the amount of force between themating surfaces 102 is approximately 15 grams.

In FIG. 11, the user has continued to turned the sleeve 26. As theelbows 84 pass the bottom of the throat surface 48, they trigger thetiming circuit 60 by electrically connecting the start panels 64. As theescapement 20 continues downward movement, the mating surfaces 102remain held together by the viscoelasticity of the saliva sample on themating surfaces 102. In FIG. 12, the escapement 20 has reached the endof its travel. Eventually, the force of the spring 92 overcomes theviscoelasticity of the saliva sample, and the mating surfaces 102separate. When the mating surfaces 102 separate, the elbows 94electrically connect the stop panels 66, signaling the timing circuit 60to discontinue timing and to indicate the result of the measurement onthe LED's 70, 72.

The Plates

The plates each have a mating surface. The mating surface may be flat orcurved. If curved, the surface of one of the plates is convex and theother is concave, with the same radius of curvature. When the matingsurfaces are in contact, as described above, the area of contact issubstantially the entire surface area of the plates. Preferably, theplates are approximately round with a surface diameter of between 0.5and 0.7 centimeters (cm), which is a surface area of approximately 0.2to 0.4 cm². The plates are between 0.2 and 0.5 cm thick.

FIG. 13 is a low-power (10×) microphotograph and FIG. 14 is a high-power(40×) microphotograph of a typical plate surface. As can be seen, theplate surface is rough; it is composed of a random distribution ofirregularly shaped valleys and ridges. The height from the floor of avalley to the peak of a ridge is approximately from 0.05 mm to 0.08 mm.

The plates surfaces are roughened so that the saliva sample willfracture internally before it separates from the plate surface. Theforce of adhesion of the sample to the surfaces must be greater than theforce of cohesion of the sample (the amount of force needed to fracturethe sample), otherwise the sample will break away from the surfacebefore it fractures, invalidating the measurement.

The plates can be composed of glass or, most preferably, a plastic. Inthe case of glass, the surface is ground to the above-describedroughened surface. In the case of plastic, the surface is etched into amold from which the plate is formed, eliminating the extra grindingstep. Plastic is preferred because the escapement 20 can be molded withthe plates as integral components. Additionally, because plastic platesare formed in a mold, there is consistency from one plate to the next.

The plates are intended to be single-use disposable items. The surfacescan be used for one measurement only because the previous saliva samplewill dry in the crevices of the surface, causing a subsequentmeasurement to be invalid since the new saliva sample cannot adhereproperly to the surface.

Determination of Fertile Period

The elapsed time measured by the timing circuit 62 is the time it takesfor the force of the spring 92 to overcome the tendency of the salivasample to remain intact, the force of cohesion. The viscoelasticity ofthe saliva sample is directly related to this time measurement by thefollowing equation: ##EQU1## where the viscosity is calculated in poise(P), the separation force is measured in dynes (dy), the surface area ismeasured in square centimeters (cm²), and the separation time ismeasured in seconds (s). The separation force/surface area term is alsocalled the shear stress and the inverse of the separation time is alsocalled the shear rate.

Note that the equation is one for viscosity, rather than forviscoelasticity. When using a Newtonian fluid, such as water, theequation will calculate pure viscosity. However, saliva is anon-Newtonian fluid. In a non-Newtonian fluid, there is an element ofelastic recoil, or elasticity, along with the viscosity. Elasticityaffects the separation time and separation force of the plates. Thus,the measurements used in the above equation are affected by theelasticity of the saliva sample. Because there is no specific equationfor viscoelasticity, the equation for viscosity is used, and theviscoelasticity is measured in viscosity-equivalent units, giving aNewtonian equivalent of the combination of viscosity and elasticityfound in the non-Newtonian saliva sample.

The portions of the calculated viscoelasticity attributed to theviscosity and to the elasticity depend upon the thickness of the saliva(density and breadth). As the thickness increases, the portionattributed to viscosity increases as a percentage of theviscoelasticity. For example, in a very thick fluid, the proportion ofviscosity to elasticity may be 80% to 20%, while in a very thin fluid,the proportion may be 20% to 80%.

Another factor to consider is that, not only do the proportions ofviscosity and elasticity change as a fluid thickens, but the absolutevalues of the viscosity and elasticity also changes. For example, athick fluid may have 80% of its viscoelasticity attributed to viscosityand 20% attributed to elasticity with absolute numbers of 64 poiseattributed to viscosity and 16 poise attributed to elasticity, and athin fluid may have 20% of its viscoelasticity attributed to viscosityand 80% attributed to elasticity with absolute numbers of 5 poiseattributed to viscosity and 20 poise attributed to elasticity.

The preferred size of the plate surfaces 102 is between about 0.2 cm²and 0.4 cm². However, in order for the saliva sample to fracture beforeit separates from the plate surfaces 102, the plate surfaces 102 areroughened to about twice the nominal surface area, namely from about 0.4cm² to about 0.8 cm². A predetermined constant pressure is appliedbetween the plate surfaces 102 for a minimum period of time ofapproximately 2 to 4 seconds when the elbows 84 are within the throat52. This pressure compresses and extrudes the saliva sample between theplate surfaces 102. After the elbows 84 are beyond the throat 52, thepressure of the spring 92 acts to fracture the saliva sample. The springforce is set to about 0.001 dy, giving a shear stress of between about0.0013 dy/cm² and 0.0025 dy/cm². The shear stress is divided by theinverse of the amount of time measured by the timer 62 to arrive at theviscoelasticity of the saliva sample. For example, if the shear stressis 0.0017 dy/cm² and the separation time is measured as 30 seconds, theviscoelasticity is calculated as 0.051 P or 5.1 centipoise (cP).

There are several different types of saliva, including sublingual andsubmandibular. The saliva pool under the tongue, the preferred source ofsaliva for the present invention, is composed in large part ofsublingual saliva with some small part of submandibular. The smallamount of submandibular saliva in the saliva pool under the tongue doesnot significantly affect the viscoelasticity of the sublingual saliva.The curve of FIG. 15 shows how the viscoelasticity of sublingual salivarelates to the fertile period. The viscoelasticity falls over a periodof from 2 to 4 days until about 16 to 24 hours prior to ovulation andthen rises over a period of from 1 to 2 days. Note that aviscoelasticity of 5.1 cP shows that the women is either about 2 daysprior to ovulation or immediately after ovulation.

Operation

The instrument 10 is designed so that the escapement 20 is disposable.Prior to usage, a new escapement 20 is acquired and inserted into thesheath 12. If the snap embodiment of FIG. 7 is used, the escapement 20is pushed into the cavity 40 until the male component 106 snaps into thefemale component 108. If the tongue embodiment of FIG. 8 is used, theescapement 20 is pushed into the cavity 40 until the tongues 112 snap upover the spring 92 of the escapement 20. During the insertion process,care must be taken to avoid contaminating the plate surfaces 102 withany foreign substance, as such contamination will invalidate themeasurement.

After the escapement 20 is in place within the sheath 12, the plates 100are dipped into the mouth in order to retrieve a sample of saliva fromthe saliva pool under the tongue. The saliva should cover substantiallythe entire plate surface 102. After taking the saliva sample, the sleeve26 is turned its full range in a relatively smooth motion. If arelatively motion is not maintained or the sleeve 26 is not turned itsfull range, an invalid measurement may result. After a period of time,one of the LED's 70, 72 will illuminate momentarily. If one LED 70illuminates, it is between approximately 48 hours and 5 hours beforeovulation. If the other LED 72 illuminates, it is not within that timeperiod before ovulation.

The escapement 20 is removable for disposal. To remove the escapement20, the sleeve 26 is turned so that the piston 24 is at its upper limitand the escapement 20 is extending from the sheath 12. The escapement 20manually pulled hard enough to separate the snap components 106, 108 orto pull the escapement 20 from the tongues 112. The escapement 20 isthen manually removed and disposed of.

In alternate embodiment, the entire instrument is disposable. In thisembodiment, the instrument is acquired with the escapement alreadyinstalled. After being used for a single measurement, the instrument isdisposed of properly.

Thus it has been shown and described an instrument for measuring salivaviscoelasticity to determine a woman's fertile period which satisfiesthe objects set forth above.

Since certain changes may be made in the present disclosure withoutdeparting from the scope of the present invention, it is intended thatall matter described in the foregoing specification and shown in theaccompanying drawings be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. An instrument for determining female fertileperiod by measuring the viscoelasticity of saliva, said devicecomprising:(a) an elongated sheath having a length along an axis and anopening at one extremity, said sheath including a barrel, a piston thatreciprocates axially within said barrel, and a rotating control formoving said piston axially within said barrel; (b) an escapementincluding a pair of elongated arms disposed approximately parallel tosaid axis, said arms having inner extremities remote from said openingand attached to said piston, and outer extremities in the vicinity ofsaid opening, said outer extremities having mating surfaces; (c) saidescapement including a spring bias urging separation of said matingsurfaces from each other; (d) said arms being mounted for relativemovement of said mating surfaces among first relational positions atwhich said mating surfaces are separated, second relational positions atwhich said mating surfaces are in contact, and third relationalpositions at which said mating surfaces are free to separate under saidspring bias; (e) said piston axial motion optionally placing said matingsurfaces into said first relational positions, said second relationalpositions, and said third relational positions; (f) at least one of saidmating surfaces being free to collect said saliva when said matingsurfaces are in said first relational positions; (g) said matingsurfaces being constrained to compress said saliva therebetween whensaid mating surfaces are in said second relational positions; and (h) atimer for measuring the time elapsed for separation of said surfaceswhen said surfaces are in said third relational positions.
 2. Theinstrument of claim 1 wherein said saliva is a combination of sublingualand mandibular saliva.
 3. The instrument of claim 1 wherein saidescapement is removable for disposal and replacement.
 4. The instrumentof claim 1 wherein each of said outer extremities includes a plate, saidmating surface being on said plate.
 5. The instrument of claim 1 whereinsaid mating surfaces are adapted to retain said saliva in a manner thatcauses said saliva to internally fracture before said saliva overcomesits adhesion to said mating surfaces.
 6. The instrument of claim 1wherein said spring bias is produced at a junction at said innerextremities of said arms.
 7. The instrument of claim 1 wherein saidsheath includes a camming mechanism for moving said mating surfaces fromsaid first relational position into said second relational positions andfrom said second relational positions to said third relationalpositions.
 8. The instrument of claim 7 wherein said camming mechanismincludes opposing elbows on said arms and a throat within said sheathaligned with said axis, whereby the movement of said elbows into saidthroat causes said mating surfaces to move from said first relationalpositions to said second relational positions and the movement of saidelbows out of said throat causes said mating surfaces to move from saidsecond relational positions to said third relational positions.
 9. Theinstrument of claim 1 wherein said timer is an electronic circuit. 10.The instrument of claim 1 wherein said timer includes a visualindicator.
 11. An instrument for determining female fertile period bymeasuring the viscoelasticity of saliva, said device comprising:(a) anelongated sheath having a length along an axis and an opening at oneextremity, said sheath including a barrel, a piston that reciprocatesaxially within said barrel, and a rotating control for moving saidpiston axially within said barrel; (b) an escapement including a pair ofelongated arms disposed approximately parallel to said axis, said armshaving inner extremities remote from said opening and attached to saidpiston, and outer extremities in the vicinity of said opening, saidouter extremities having mating surfaces that are adapted to retain saidsaliva in a manner that causes said saliva to internally fracture beforesaid saliva overcomes its adhesion to said mating surfaces; (c) saidescapement including a spring bias urging separation of said matingsurfaces from each other; (d) said arms being mounted for relativemovement of said mating surfaces among first relational positions atwhich said mating surfaces are separated, second relational positions atwhich said mating surfaces are in contact, and third relationalpositions at which said mating surfaces are free to separate under saidspring bias; (e) said piston axial motion optionally placing said matingsurfaces into said first relational positions, said second relationalpositions, and said third relational positions; (f) said sheathincluding a camming mechanism for moving said mating surfaces from saidfirst relational position into said second relational positions and fromsaid second relational positions to said third relational positions; (g)at least one of said mating surfaces being free to collect said salivawhen said mating surfaces are in said first relational positions; (h)said mating surfaces being constrained to compress said salivatherebetween when said mating surfaces are in said second relationalpositions; and (i) an electronic circuit for measuring the time elapsedfor separation of said surfaces when said surfaces are in said thirdrelational positions, said circuit including a visual indicator.
 12. Theinstrument of claim 11 wherein said escapement is removable for disposaland replacement.
 13. The instrument of claim 11 wherein each of saidouter extremities includes a plate, said mating surface being on saidplate.
 14. The instrument of claim 11 wherein said spring bias isproduced at a junction at said inner extremities of said arms.
 15. Theinstrument of claim 11 wherein said camming mechanism includes opposingelbows on said arms and a throat within said sheath aligned with saidaxis, whereby movement of said elbows into said throat causes saidmating surfaces to move from said first relational positions to saidsecond relational positions and movement of said elbows out of saidthroat causes said mating surfaces to move from said second relationalpositions to said third relational positions.
 16. An instrument fordetermining female fertile period by measuring the viscoelasticity ofsaliva, said device comprising:(a) an elongated sheath having a lengthalong an axis and an opening at one extremity, said sheath including abarrel, a piston that reciprocates axially within said barrel, and arotating control for moving said piston axially within said barrel; (b)an escapement including a pair of elongated arms disposed approximatelyparallel to said axis, said arms having inner extremities remote fromsaid opening and removably attached to said piston, and outerextremities in the vicinity of said opening, said outer extremitieshaving mating surfaces that are adapted to retain said saliva in amanner that causes said saliva to internally fracture before said salivaovercomes its adhesion to said mating surfaces; (c) a junction at theinner extremities of said arms producing a spring bias urging separationof said mating surfaces from each other; (d) said arms being mounted forrelative movement of said mating surfaces among first relationalpositions at which said mating surfaces are separated, second relationalpositions at which said mating surfaces are in contact, and thirdrelational positions at which said mating surfaces are free to separateunder said spring bias; (e) said piston axial motion optionally placingsaid mating surfaces into said first relational positions, said secondrelational positions, and said third relational positions; (f) saidsheath including a camming mechanism for moving said mating surfacesfrom said first relational position into said second relationalpositions and from said second relational positions to said thirdrelational positions; (g) said camming mechanism including opposingelbows on said arms and a throat within said sheath aligned with saidaxis, whereby movement of said elbows into said throat causes saidmating surfaces to move from said first relational positions to saidsecond relational positions and movement of said elbows out of saidthroat causes said mating surfaces to move from said second relationalpositions to said third relational positions; (h) at least one of saidmating surfaces being free to collect said saliva when said matingsurfaces are in said first relational positions; (i) said matingsurfaces being constrained to compress said saliva therebetween whensaid mating surfaces are in said second relational positions; and (j) anelectronic circuit for measuring the time elapsed for separation of saidsurfaces when said surfaces are in said third relational positions, saidcircuit including a visual indicator.